Carbon corrosion mechanism on nitrogen-doped carbon support — A density functional theory study

Li, Yunqi; Li, Jing; Wang, Yang‐Gang; Chen, Xiran; Liu, Mingtao; Zheng, Zhong; Peng, Xihong

doi:10.1016/j.ijhydene.2021.01.148

Cited by 18 publications

(11 citation statements)

References 48 publications

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“…N-functionalities in the carbon matrix are discussed to increase its stability against electrochemical oxidative corrosion as recently reported by our group [30]. Additionally, pyrrolic, pyridinic and graphitic N are known to increase the stability because they destabilize surface oxides which are formed during carbon corrosion [31]. However, in our study we observed no correlation of the amount of N-functionalities with the stability of the catalyst, since the N-groups content is similar across all catalysts but the stability differs as discussed above.…”

Section: Stress Test Induced Changesmentioning

confidence: 80%

Elucidating Synergistic Effects of Different Metal Ratios in Bimetallic Fe/Co-N-C Catalysts for Oxygen Reduction Reaction

et al. 2021

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Lowering or eliminating the noble-metal content in oxygen reduction fuel cell catalysts could propel the large-scale introduction of commercial fuel cell systems. Several noble-metal free catalysts are already under investigation with the metal-nitrogen-carbon (Me-N-C) system being one of the most promising. In this study, a systematic approach to investigate the influence of metal ratios in bimetallic Me-N-C fuel cells oxygen reduction reaction (ORR) catalysts has been taken. Different catalysts with varying ratios of Fe and Co have been synthesized and characterized both physically and electrochemically in terms of activity, selectivity and stability with the addition of an accelerated stress test (AST). The catalysts show different electrochemical properties depending on the metal ratio such as a high electrochemical mass activity with increasing Fe ratio. Properties do not change linearly with the metal ratio, with a Fe/Co ratio of 5:3 showing a higher mass activity with simultaneous higher stability. Selectivity indicators plateau for catalysts with a Co content of 50% metal ratio and less, showing the same values as a monometallic Co catalyst. These findings indicate a deeper relationship between the ratio of different metals and physical and electrochemical properties in bimetallic Me-N-C catalysts.

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Section: Stress Test Induced Changesmentioning

confidence: 80%

Elucidating Synergistic Effects of Different Metal Ratios in Bimetallic Fe/Co-N-C Catalysts for Oxygen Reduction Reaction

et al. 2021

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“…Furthermore, nitrogen doping and, especially, the presence of pyrrolic N species are reported to increase the resistance toward carbon corrosion . Pyrrolic, pyridinic, and graphitic N can lead to unstable intermediates of surface oxides during the carbon corrosion mechanism and thus to an increase in stability . For further analysis of stability, identical-location (IL-)TEM was carried out for the Fe-N-ox-BP catalyst because this catalyst showed the highest MA loss after the AST.…”

Section: Results and Discussionmentioning

confidence: 99%

“…31 Pyrrolic, pyridinic, and graphitic N can lead to unstable intermediates of surface oxides during the carbon corrosion mechanism and thus to an increase in stability. 68 For further analysis of stability, identical-location (IL-)TEM was carried out for the Fe-N-ox-BP catalyst because this catalyst showed the highest MA loss after the AST. Through IL-TEM, it is possible to observe the same location before and after the AST.…”

Section: Resultsmentioning

confidence: 99%

Incorporation of Activated Biomasses in Fe-N-C Catalysts for Oxygen Reduction Reaction with Enhanced Stability in Acidic Media

Müller-Hülstede

Schonvogel

Schmies

et al. 2021

ACS Appl. Energy Mater.

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Fe-N-C materials are promising oxygen reduction reaction (ORR) catalysts for replacing expensive platinum-based catalysts (Pt/C) in proton exchange membrane fuel cells. However, they still show low volumetric activity and stability compared to Pt/C catalysts, with carbon corrosion being one of the main factors for the loss of active Fe-N x sites. Within this study, phosphoric acid-activated rye straw and coconut shells are revealed as a promising matrix for Fe-N x sites with advanced stability against electrochemical carbon corrosion (5000 cycles, 1.0–1.5 VRHE, and 0.1 M HClO4) compared to a common Fe-N-C catalyst based on carbon black. Electrochemical characterization of the two biomass-based catalysts (Fe-N-CBio) shows on the one hand 50% higher stability in terms of mass activity as well as comparable activity and active site density but on the other hand a lower selectivity toward the four-electron ORR than the common Fe-N-C catalyst. Nitrite stripping experiments in acetate buffer as an electrolyte display a 1.5-fold stronger effect of carboxylic acid adsorption than on a common Fe-N-C catalyst, revealing differences to the electronic structure of the Fe-N-CBio catalyst. This difference is mainly attributed to the presence of phosphor species and higher amounts of nitrogen functionalities in the Fe-N-CBio catalysts. The presence of P is assumed to stabilize the carbon against carbon corrosion by inhibiting electron withdrawal from the C. This study points out the impact factors on Fe-N-C stability and further shows the promising application of activated biomasses in more stable and sustainable Fe-N-C catalysts for ORR.

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“…Although a boosting effect of N‐doping was found, [25] where the researchers suggested that the active sites for ORR/OER are close to the carbon adjacent to the pyridinic N, no clear evidence for one specific active species is found yet. Moreover, the corrosion or degradation of carbon‐based OER catalysts were not well studied and are rarely considered in literature [26–29] . Also with respect to stability, the nature of the functional groups were proposed to influence the stability, for instance pyrrolic and pyridinic N sites were calculated to be more stable than graphitic N [29] .…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, the corrosion or degradation of carbon‐based OER catalysts were not well studied and are rarely considered in literature [26–29] . Also with respect to stability, the nature of the functional groups were proposed to influence the stability, for instance pyrrolic and pyridinic N sites were calculated to be more stable than graphitic N [29] . Here, we demonstrate that indeed nitrogen species in the carbonaceous electrode not only provide active functional groups for the OER, but also slow down the carbon corrosion process, leading to an improved selectivity towards O 2 instead of CO or CO 2 [30] .…”

Section: Introductionmentioning

confidence: 99%

Binder‐Free N‐Functionalized Carbon Electrodes for Oxygen Evolution Reaction

et al. 2023

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The oxygen evolution reaction (OER) is one of the bottlenecks of electrochemical water splitting. Metal‐free carbons from biomass are highly abundant and can be easily synthesized. Their low price, high conductivity and functionalization makes them promising materials. Herein, we report about free‐standing carbon electrodes as electrocatalysts for the OER. In contrast to powder‐based catalysts, free‐standing electrodes not only avoid additives, but also facilitate post analysis and better reflect industrial conditions. Here, the performance of pure carbon electrodes is compared to those of N‐functionalized ones. Utilizing several analytical techniques, the difference in performance can be rationalized by physical properties. Especially, the analysis of the gaseous products is shown to be of crucial importance. It reveals that N‐doped carbons generate more oxygen and are more robust against carbon corrosion. This illustrates the importance of measuring selectivity especially for carbon electrocatalysts, as higher currents do not necessarily result in higher catalytic activity.

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Carbon corrosion mechanism on nitrogen-doped carbon support — A density functional theory study

Cited by 18 publications

References 48 publications

Elucidating Synergistic Effects of Different Metal Ratios in Bimetallic Fe/Co-N-C Catalysts for Oxygen Reduction Reaction

Elucidating Synergistic Effects of Different Metal Ratios in Bimetallic Fe/Co-N-C Catalysts for Oxygen Reduction Reaction

Incorporation of Activated Biomasses in Fe-N-C Catalysts for Oxygen Reduction Reaction with Enhanced Stability in Acidic Media

Binder‐Free N‐Functionalized Carbon Electrodes for Oxygen Evolution Reaction

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